- SO2F2-Mediated Oxidative Dehydrogenation and Dehydration of Alcohols to Alkynes
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Direct synthesis of alkynes from inexpensive, abundant alcohols was achieved in high yields (greater than 40 examples, up to 95% yield) through a SO2F2-promoted dehydration and dehydrogenation process. This straightforward transformation of sp3-sp3 (C-C) bonds to sp-sp (C=C) bonds requires only inexpensive and readily available reagents (no transition metals) under mild conditions. The crude alkynes are sufficiently free of impurities to permit direct use in further transformations, as illustrated by regioselective Huisgen alkyne-azide cycloaddition reactions with PhN3 to give 1,4-substituted 1,2,3-traiazoles (16 examples, up to 92% yield) and Sonogashira couplings (10 examples, up to 77% yield).
- Zha, Gao-Feng,Fang, Wan-Yin,Li, You-Gui,Leng, Jing,Chen, Xing,Qin, Hua-Li
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supporting information
p. 17666 - 17673
(2019/01/04)
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- Synthesis and biological activity of alkynoic acids derivatives against mycobacteria
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2-Alkynoic acids have bactericidal activity against Mycobacterium smegmatis but their activity fall sharply as the length of the carbon chain increased. In this study, derivatives of 2-alkynoic acids were synthesized and tested against fast- and slow-growing mycobacteria. Their activity was first evaluated in M. smegmatis against their parental 2-alkynoic acids, as well as isoniazid, a first-line antituberculosis drug. The introduction of additional unsaturation or heteroatoms into the carbon chain enhanced the antimycobacterial activity of longer chain alkynoic acids (more than 19 carbons long). In contrast, although the modification of the carboxylic group did not improve the antimycobacterial activity, it significantly reduced the toxicity of the compounds against eukaryotic cells. Importantly, 4-(alkylthio)but-2-ynoic acids, had better bactericidal activity than the parental 2-alkynoic acids and on a par with isoniazid against the slow-grower Mycobacterium bovis BCG. These compounds had also low toxicity against eukaryotic cells, suggesting that they could be potential therapeutic agents against other types of topical mycobacterial infections causing skin diseases including Mycobacterium abscessus, Mycobacterium ulcerans, and Mycobacterium leprae. Moreover, they provide a possible scaffold for future drug development.
- Vilchze, Catherine,Leung, Lawrence W.,Bittman, Robert,Jacobs, William R.
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p. 125 - 138
(2016/01/25)
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- Total synthesis of (-)-goniotrionin
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A stereoselective total synthesis of the reported structure of goniotrionin (4) has been accomplished. The key steps involved the opening of a chiral epoxide, a highly diastereoselective Mukaiyama aerobic oxidative cyclization, a selective 1,2-syn Mukaiyama aldol reaction, and a Noyori reduction.
- Dias, Luiz C.,Ferreira, Marco A. B.
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p. 4046 - 4062
(2012/06/29)
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- Structural confirmation of the dihydrosphinganine and fatty acid constituents of the dental pathogen Porphyromonas gingivalis
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Porphyromonas gingivalis, a recognized periodontal pathogen, is a source of sphinganine bases, fatty acids, free ceramides as well as complex lipids that potentiate interleukin-1b-mediated secretory responses in gingival fibroblasts. The purpose of this study is the structural verification of the sphinganine bases and fatty acids that had been proposed as major components of the complex lipids found in P. gingivalis. The putative C17, C18, and C19 sphinganine bases were prepared from Garner's aldehyde (1) or from a protected serine Weinreb's amide (2). We confirmed that isobranched sphinganine bases are the major structural feature of the ceramides observed from P. gingivalis. We also prepared a C17 unsaturated fatty acid, along with an isobranched C17 3-hydroxy fatty acid, and determined that the major component of the active lipids was the latter. The Royal Society of Chemistry 2007.
- Mun, JiYoung,Onorato, Amber,Nichols, Frank C.,Morton, Martha D.,Saleh, Abdullah I.,Welzel, Morgan,Smith, Michael B.
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p. 3826 - 3833
(2008/10/09)
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- Claisen rearrangements based on vinyl fluorides
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2-Fluoroalk-1-en-3-ols (4), available from terminal alkenes (1) by bromofluorination, subsequent dehydrobromination of the 1-bromo-2-fluoroalkanes (2) to form 2-fluoroalkenes (3) and selenium dioxide mediated allylic oxidation with tert-butylhydroperoxide, undergo Johnson-Claisen rearrangement on treatment with trimethyl orthoacetate to give methyl 4-fluoroalk-4-enoates (7) in high yields. In contrast Ireland-Claisen rearrangement of 3-acetoxy-2-fluorodec-1-ene (9b) with triethylamine and TMSOTf in ether failed. Instead of the expected formation of a carboxylic acid, selective C-silylation of the α-position to the carboxyl group to form 14 occurred. However, Ireland-Claisen rearrangement was successful with corresponding chloroacetates 10 and propionates 11 of four 2-fluoroalk-1-en-3-ols (4) to give 2-chloro-4-fluoroalk- 4-enecarboxylic acids (15) or its 2-methyl derivatives 16, respectively, in moderate yields. These [3,3]-sigmatropic rearrangements are diastereoselective giving trans-configured double bonds, exclusively. Corresponding esters derived from (Z)-2-fluorocyclododec-2-enol (22), did rearrange to yield mixtures of diastereomers much less selectively. Also 2-fluorodec-2-enol (6), which was prepared by rearrangement of 2-fluoro-2-octyloxirane (5) with TMSOTf and triethylamine, was successfully applied as a starting material for [3,3]-sigmatropic rearrangements. The corresponding 3-(1-fluoroethenyl)alkanoic acid derivatives 17 and 18 were formed in moderate yield. 2-Fluoroalk-1-en-3-ol esters prepared in two steps from 2-fluoroalk-1-enes undergo Claisen rearrangements to form 2-substistuted 4-fluoroalk-4-enecarboxylic acids.
- Tranel, Frank,Haufe, Günter
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p. 1593 - 1608
(2007/10/03)
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- SYMMETRICAL AND UNSYMMETRICAL COUPLING OF ALKYL HALIDES MEDIATED BY GRIGNARD REACTION
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A simple method for extending the carbon chain via the coupling of alkyl or aryl halides has been developed.The versatility of this reaction has been demonstrated by symmetrical and unsymmetrical coupling of alkyl, alkenyl or alkynyl halides.
- Herendeen, Barbara L.,Bhatia, Suresh K.,Singh, Alok
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p. 2899 - 2908
(2007/10/02)
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- A CONVENIENT ROUTE TO ALKYNES VIA PHASE TRANSFER CATALYSIS; ( APPLICATIONS OF PHASE TRANSFER CATALYSIS, PART 19 )
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High yield, rapid formations of alkynes from vic-dibromides are possible using powered potassium hydroxide and catalytic amounts of lipophilic phase transfer catalysts.Reasons are given why molar amounts of expensive catalysts were necessary in earlier procedures.
- Dehmlow, Eckehard V.,Lissel, Manfred
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p. 1653 - 1658
(2007/10/02)
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- Application of Phase Transfer Catalysis, 14.- Preparation of Alkynes from Halides with Solid Potassium tert-Butoxide and Crown Ether
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Preparatively very simple and mild HX eliminations with solid potassium tert-butoxide in petroleum ether in the presence of catalytic amounts of crown-6 are described. 1,2-Dihalides (from alkenes) and 1,1-dihalides (from aldehydes) yield 1-alkynes; internal geminal dihalides (from symmetric ketones) give internal alkynes in excellent yields. 2,2-Dihalides (from methyl ketones) yield homogeneous 1-alkynes only if the 3-position is blocked. (E)-Haloalkenes lead also to alkynes in a syn-elimination process.
- Dehmlow, Eckehard V.,Lissel, Manfred
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- Synthesis of high specific activity tritium-labelled dotriacontane
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The tobacco smoke particulate phase marker dotriacontane was labelled with tritium at positions 15, 16, 17 and 18 by the catalytic reduction of dotriaconta-15, 17-diyne. This was obtained by oxidatively coupling hexadec-1-yne, in turn prepared by reaction of monosodium acetylide with myristyl bromide.
- Houseman,Binns,Phillips
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p. 163 - 167
(2007/10/05)
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